The present invention generally relates to schemes for detecting bonding status of a bonding wire of a semiconductor package, particularly a package in which the resistance resulting from the adhesion layer and Cupric Oxide layer between the semiconductor unit (such as a chip or die) and its carrier is not low enough for forming a current loop.
The electrical connection status between a bonding wire and a semiconductor unit as well as that between the bonding wire and a solder ball pad in a package shall always be checked to see if it is good after wire bonding process. As shown in FIG. 1, after bonding wire 35 was bonded to a bonding pad 6 (or called wire bonding pad) of a semiconductor unit 1 to make an electrical connection between the bonding wire 35 and the semiconductor unit 1, it is bonded to bonding finger 10, which is followed by cutting off the bonding wire 35 at a proper position (such as the location slightly left to the point 18 in the figure), so that the capillary 24 of wire bonding machine may continue bonding another bonding wire to another wire bonding pad of semiconductor unit 1. After capillary 24 completes bonding wire bonding pad 6 by bonding wire 35, wire bonding machine applies an electrical potential difference between bonding wire 35 and a press plate 14, thereby a current is expected to flow through bonding wire 35 (the part between capillary 24 and bonding pad 6), bonding pad 6, semiconductor unit 1, conductive adhesion layer 2, heat dissipater 3, and hot plate 14 back to the wire bonding machine to form a loop current (the direction shown by arrows 45, 46, and 47 is a possible current flowing direction). In case the bonding status between bonding wire 35 and bonding pad 6 is not good, the loop current will be very small or negligible as a result of bad electrical connection between bonding wire 35 and wire bonding pad 6. A normal loop current resulting from normal bonding status will thus be indicative of the good bonding status (good electrical connection) between bonding wire 35 and semiconductor unit 1.
Shown in FIG. 2 is a conventional art in which a layer 4 of Cupric Oxide is coated on a surface of heat dissipater 3 in order to enhance the adhesive force between heat dissipater 3 and semiconductor unit 1, encapsulant body, as well as substrate 7, resulting in the infeasibility of forming the loop current because the layer 4 of cupric oxide is nonconductive. This is why the current direction represented by arrow 47 of FIG. 1 does not exist in FIG. 2, leading to the extreme difficulty of detecting the bonding status (or called electrical connection status) between bonding wire and semiconductor unit in a package, particularly during wire bonding process.
Although the arts disclosed by U.S. Pat. Nos. 5,712,570 and 5,893,508 are also used for detecting the bonding status of bonding wire in a semiconductor package, they are subject to a condition: chip and its carrier or some devices on its carrier form a conductive path for a current loop, therefore these arts cannot be applicable to the case illustrated in FIG. 2 where the layer 4 of Cupric Oxide or the adhesion layer 2 is not electrically conductive. The present invention is thus developed to resolve the problem resulting from either the nonconductive layer of Cupric Oxide or the nonconductive adhesion layer, and thereby to provide convenience for related industries to take advantage of the benefit of the layer of Cupric Oxide, while still be able to detect the bonding status of a bonding wire when packaging a Ball Grid Array package or similar types of packages, leading to more convenient, more systematic, and more flexible operation for detecting the bonding status of bonding wires in a semiconductor package, particularly during wire bonding process.
An object of the present invention is to provide a method associated with a wire bonding machine or a wire bonding process, for detecting bonding status of a bonding wire of a Ball Grid Array package or similar types of packages (such as those with solder ball pads thereof located on the same surface of a substrate as are semiconductor units thereof), the method achieving more convenient, more systematic, more flexible or less confined (allows the existence of insulation between semiconductor unit and its carrier, for example) schemes for detecting bonding status of a bonding wire, particularly for detecting abnormal bonding status during wire bonding process in order to make up it early enough.
Another object of the present invention is to provide a system associated with a wire bonding machine or a wire bonding process, for detecting bonding status of a bonding wire of a Ball Grid Array package or similar types of packages (such as those with solder ball pads thereof located on the same surface of a substrate as are semiconductor units thereof), the system achieving more convenient, more systematic, more flexible or less confined (allows the existence of insulation between semiconductor unit and its carrier, for example) schemes for detecting bonding status of a bonding wire, particularly for detecting abnormal bonding status during wire bonding process in order to make up it early enough.
A further object of the present invention is to provide the industries related to Ball Grid Array package or similar types of packages, with the convenience or flexibility of selecting, according to individual requirements or conditions, proper schemes for detecting the bonding status of bonding wires of a package. For example, it provides convenience or flexibility of selecting from among the three schemes: only detecting the bonding status between bonding wire and semiconductor unit, only detecting the electrical connection status between bonding wire and solder ball pad, and detecting both the above.
The present invention may be represented by a system associated with a wire bonding process, for detecting bonding status of at least a bonding wire of a package including at least a semiconductor unit and at least a package-connection-means such as solder ball pad. The system primarily comprises: at least a carrier such as a substrate, a heat dissipater, or a piece of tape, or any object capable of supporting the semiconductor unit and/or package-connection-means; at least an electrical conduction means such as an object made of electrically conductive metal, or electrically conductive rubber, or anisotropically conductive film, or the combination of these material, the electrical conduction means contacting at least a selected one of the package-connection-means; at least a preset connection means such as an electrical connection system (an electric wire or a system composed of a trace, a bonding finger, and a bonding wire, for example) established in the beginning of the wire bonding process, for electrically connecting the selected one of the package-connection-means and the semiconductor unit; a voltage source which may be a direct or alternate source or a capacitor, for providing an electrical potential difference between the electrical conduction means and the bonding wire; and a detector such as a current meter, for measuring, when the bonding wire is so bonded (by the wire bonding process, for example) as to electrically connect at least one of the semiconductor unit and the package-connection-means, a current passing the voltage source, and for providing, according to the measured current, at least a status indicating signal reflecting the bonding status (or electrical connection status) between the bonding wire and the semiconductor unit, and/or the bonding status (or electrical connection status) between the bonding wire and a component which may be a bonding finger on the carrier supporting the package-connection-means, and which electrically connects the package-connection-means via the carrier (a trace on the carrier, for example) supporting the package-connection-means.
The present invention may also be represented by a method associated with a wire bonding machine, for detecting bonding status of a bonding wire of a package including at least a semiconductor unit and at least a package-connection-means such as solder ball pad, wherein the semiconductor unit and the package-connection-means are supported by at least a carrier with the wire bonding pads of the semiconductor unit exposed. The method may comprise the steps of: selecting at least one of the package-connection-means such as sold ball pads to be contacted by an electrical conduction means such as an object made of electrically conductive metal, or electrically conductive rubber, or anisotropically conductive film, or the combination of these material; electrically connecting the semiconductor unit and the selected one of the package-connection-means; letting a press plate of the wire bonding machine contact the electrical conduction means; using a voltage source to provide an electrical potential difference which exists between the press plate and the bonding wire when the wire bonding machine completes bonding the bonding wire to the semiconductor unit; measuring a current passing the voltage source, and providing a status indicating signal according to the measured current to reflect the bonding status between the bonding wire and the semiconductor unit. An embodiment of the above step of electrically connecting the semiconductor unit and the selected one of the package-connection-means may be to bond a wire to the semiconductor unit and a bonding finger connecting the package-connection-means via a trace of the carrier supporting the package-connection-means.
The present invention may further be represented by a second method also associated with a wire bonding machine, for detecting bonding status of a bonding wire of a package including at least a semiconductor unit and at least a package-connection-means such as solder ball pad, wherein the semiconductor unit and the package-connection-means are supported by at least a carrier with the wire bonding pads of the semiconductor unit exposed. The second method may comprise the steps of: contacting all of the package-connection-means by an electrical conduction means such as an object made of electrically conductive metal, or electrically conductive rubber, or anisotropically conductive film, or the combination of these material; selecting at least one of the package-connection-means to electrically connect the semiconductor unit; letting a press plate of the wire bonding machine contact the electrical conduction means; using a voltage source to provide an electrical potential difference which exists between the press plate and the bonding wire when the wire bonding machine completes bonding the bonding wire to the semiconductor unit, and also exists when the wire bonding machine completes bonding the bonding wire to a component (a bonding finger of the carrier supporting the package-connection-means, for example) electrically connecting the package-connection-means; and measuring twice the current passing the voltage source, and providing a first status indicating signal according to the current measured at the first time to reflect the bonding status between the bonding wire and the semiconductor unit, then providing a second status indicating signal according to the current measured at the second time to reflect the electrical connection status between the bonding wire and the package-connection-means, or the bonding status between the bonding wire and the component electrically connecting the package-connection-means.
The present invention may best be understood through the following description with reference to the accompanying drawings, in which: